We develop the dynamical core-corona initialization framework as a phenomenological description of the quark gluon plasma (QGP) fluids formation in high-energy nuclear collisions. Using this framework, we investigate the fraction of the fluidized energy to the total energy and strange hadron yield ratios as functions of multiplicity and scrutinize the multiplicity scaling of hadron yield ratios recently reported by ALICE Collaboration. Our results strongly indicate that the QGP fluids are partly formed even at the averaged multiplicity for non-single diffractive p+p events.
We investigate the enhancement of yields of strange and multi-strange baryons in proton-proton (p+p), proton-lead (p+Pb) and lead-lead (Pb+Pb) collisions at the Large Hadron Collider (LHC) energies from a dynamical core-corona initialization model. We first generate partons just after the collisions by using event generators. These partons dynamically generate the quark gluon plasma (QGP) fluids through the source terms in the hydrodynamic equations. According to the corecorona picture, this process tends to happen where the density of generated partons is high and their transverse momentum is low. Some partons do not fully participate in this process when they are in dilute regions or their transverse momentum is high and subsequently fragment into hadrons through string fragmentation. In this framework, the final hadrons come from either chemically equilibrated fluids as in the conventional hydrodynamic models or string fragmentation. We calculate the ratio of strange baryons to charged pions as a function of multiplicity and find that it monotonically increases up to dN ch /dη ∼ 100 and then saturates above. This suggests that the QGP fluids are partly created and that their fraction increases with multiplicity in p+p and p+Pb collisions at LHC energies. PACS numbers: 25.75.-q, 12.38.Mh, 25.75.Ld, 24.10.Nz Introduction.-High-energy heavy-ion collision experiments are performed at the Relativistic heavy-ion Collider (RHIC), Brookhaven National Laboratory, and the Large Hadron Collider (LHC), CERN, to further understanding of the properties of deconfined nuclear matter, the quark gluon plasma (QGP) [1]. A vast body of the experimental data have been accumulated and theoretical analysis of them elucidates that the QGP behaves almost like a perfect fluid [2-6].Comparisons of data from heavy-ion collision experiments with those from control experiments such as proton-proton, proton-nucleus and deuteron-nucleus collisions could bring deeper insights into the properties of the QGP. However, high-multiplicity events in these small colliding systems exhibit some collective behaviors, which can be interpreted as creation of QGP fluids (for a review, see, e.g., Ref. [7]). In addition, enhanced production of multi-strange hadrons relative to charged pions has been measured in high-multiplicity small colliding systems [8]. Strangeness enhancement was proposed as a signature of QGP formation, [9-11] and has been observed in high-energy heavy-ion collisions [12][13][14][15][16]. The ratio of yields of multi-strange hadrons to those of charged pions monotonically increases with charged hadron multiplicity at mid-rapidity, dN ch /dη, and saturates above dN ch /dη ∼ 100 regardless of the size or collision energy of the systems [8]. In the low-multiplicity limit, the ratio can be described by string fragmentation
We present new results in p+p and Pb+Pb collisions at the LHC energies from the updated dynamical core–corona initialization framework (DCCI2). The fractions of final hadron yields originating from equilibrated and non-equilibrated components are extracted as functions of multiplicity. We find that the contributions from non-equilibrated components are non-negligible even in Pb+Pb collisions and affect pT-integrated multi-particle correlations. These suggest the importance of non-equilibrated components for the sophisticated extraction of properties of the quark gluon plasma from comparisons between dynamical frameworks and experimental data.
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